Pressure ulcers (PUs), also known as bedsores, develop at the boney prominences of the body (e.g., heel, elbow, shoulder bones, sacrum). Currently, PU prevention is one of the greatest challenges facing caregivers, hospitals, and long term care facilities. PUs occur most frequently in institutionalized, community-dwellings and nursing homes for older adults, where they are a serious problem that can lead to sepsis and death. In nursing homes, PUs represent a significant problem for residents (in terms of morbidity, pain, and reduced quality of life) and for facilities (in terms of staffing and costs of care). Once a PU develops, it is costly and extremely difficult to heal. They are very resistant to known medical therapy and, unlike acute wounds, PUs do not proceed through an orderly and timely process of healing to reduce anatomical or functional integrity. PUs cost the US health care system approximately $1.3 billion every year. The prevalence of PUs ranges from 10-17% in acute care, 0-29% in home care, and 2.3-28% in institutional long-term care (LTC). The cost to heal a complex, full-thickness PU in 2006 was as much as $70,000; the cost for a less serious PU may range from $2000 to $30,000.
The development of PUs often is viewed as negligent care by a healthcare provider or a health system. Litigation stemming from PU development and negligence is high in the US despite the fact that PU incidence is monitored and preventative measures are mandated by the government. Typical PU awards in the US range from $5,000 to $82 million, with the median award approximately $250,000. PU prevention and litigation is also a large problem in Europe.
Currently, the early diagnosis of a PU is conducted using visual and tactile investigation of the skin. The standard tactile tool used clinically is the blanch test. The blanch test involves applying gentle pressure to the skin to observe the whitening or blanching of the skin. A blanching area of reddened skin indicates healthy tissue structure and perfusion. A non-blanching area of redness is diagnosed as a stage I PU. To the inventors' knowledge, all available commercial instruments designed to measure PUs are analytical instruments intended for experimental laboratory use only. Analytical experimental devices that shine light onto the skin and collect the light reflected back to identify or determine different properties of the skin (e.g. erythema and melanin content) have been designed. Analytical commercial narrow-band reflectance instruments that can be applied to the diagnosis of stage-I PUs function by utilizing erythema/melanin indices to identify erythema across individuals with varying skin pigmentation are known. Although these devices can detect erythema in spite of skin pigmentation, they have limited utility as bedside clinical tools because they are an expensive alternative to the manual blanch test, they are large and bulky for a bedside device, and they are not simple to use for an untrained professional. Rather, they are specifically designed for cosmetology/dermatology experimental research, where quantification of experimentally induced color changes is widely performed.
Portable devices that measure non-blanchable erythema or the microcirculation properties of the skin related to pressure ulcer development are known, including U.S. Pat. No. 6,631,288 (“the '288 patent”) and U.S. Pat. No. 7,155,273 (“the '273 patent”). The devices described in these patents analyze reflected light to yield a diagnosis. They also contain varying components for applying pressure to the skin to observe blanching. The '288 patent utilizes a sliding probe that enables the reflectance data to be analyzed to monitor transient microcirculation (refill time) after blanching to infer the progression of the pressure ulcer. The '273 patent includes a specialized probe that simultaneously compares damaged and healthy tissue to get a personalized baseline for diagnosis. A major limitation of these patented designs is that the specialized probe depends on the user's skill level and ability to visually identify (the current subjective method of PU identification) the size and location of the stage I pressure ulcer (in light and dark skin), so that the probe can either be run along the length of the PU for microcirculation analysis and PU diagnosis or placed along the perimeter of the PU for simultaneous healthy and diseased tissue analysis and subsequent PU diagnosis. To the inventor's knowledge, neither of these patented designs has been successfully tested on humans or currently exist as commercial devices.